Experience shows that, in the event of an impact on one of the end pieces, or in the event of excessive outside pressure on an end piece, as can occur with air tanks for deep-sea divers, the end piece can be driven into the tank, leading to the deterioration and even the rupture of the inside shell in the area around the periphery of the end piece. Such an accident allows the fluid to escape from the inside shell and move between the latter and the outside shell, which, because of its structure, can allow the pressurized fluid to escape to the outside.